This butterfly is Vindula erota erota Fabricius, 1793: the Thai Cruiser. There are both Wet and Dry season forms of this species (1). This occurrence of different types or forms of the same butterfly species, in different seasons, is called ‘seasonal polyphenism’ and has probably evolved as an adaptation to the different environments – and the challenges they bring – in the ‘wet’ and ‘dry’ seasons of tropical regions. There is a theory (2) that in the dry season, when butterflies may spend quite a long time in a state of quiescence – waiting for the rains! –  there is a greater need for the butterflies to be cryptic or hidden, to escape from their predators. In the wet season on the other hand – which is generally a time of reproduction and egg laying – it is better to adopt colours and patterns which can startle or deflect predators. Well that’s one idea. Whatever is going on, there are wet and dry season forms in many different butterfly species, so it is clearly a useful adaptation and may involve different behaviours as well as colours (2).

The sequence of photographs shown below are of dry season, V. e. erota males photographed on the 30 November 2015 in northern Thailand (Doi Chiang Dao). The timing of the occurrence of wet and dry season forms probably varies from place to place and females are said to exhibit more seasonal variation than males (3). I posted pictures of the slightly larger female, dry season form, in a previous blog (4). The female has a prominent whitish band which extend across the upperside of both wings, in contrast to a greenish-brown background colour of the wing (below).

The male is a much brighter orange brown colour, with black and brown spots and markings and a greenish tinge to the abdomen on fresh specimens (see below).

Males are commonly seen ‘mud puddling’ – absorbing moisture and salts. Females are seen much less commonly and I did not see any in this location on this occasion. I took a series of photographs of these butterflies on a sunlit patch of concrete on the steps leading up to a temple (Wat Tham Pha Plong) on the slopes of Doi Chiang Dao, Chiang Mai Province, Thailand (below).

Whilst I was photographing the butterflies, I noticed that two males were closely associating with each other. But when I came to look at the images closely, it was apparent that they were not only absorbing liquids using their proboscises, but also secreting small amounts of liquid from the end of their abdomens. Quite what is going on, I don’t know, but it is interesting to record butterfly behaviour; there is so much we do not know about the lives of such species, and I hope this goes a small way to demonstrate the richness and complexity of the lives of living insects.

The two interacting butterflies can easily be separated, as one had a couple of small notches – no doubt as a result of pecking damage by birds – on the apex of the right forewing (below). Let’s call him ‘Notch’.

The other butterfly was by contrast unmarked, let’s call him ‘Unmarked’ (below).

Unmarked was ‘puddling’ by himself – sucking up something good, salty or satisfying – on a sunlit piece of concrete on the steps. The abdomen was also noticeably curved downwards, as we will see again more clearly, below.

Unmarked carried on supping in the sun, slowly opening and closing his wings and gradually lowering the tip of his abdomen and pressing it onto the ground.

Then along came Notch, landing next to Unmarked, and started feeding right next to him in exactly the same way.

Notch gradually moved closer to Unmarked and placed his wings exactly along side Unmarked’s wings, mirroring his position. I got the impression that they were pressing against each other. The wings were so closely aligned that it looked like they had wanted to be side by side; but what was the purpose of this behaviour? They were both engaged in absorbing something liquid from the ground.

Together they carried on feeding and pressing up against each other.

In this photograph (below), they are both dipping their proboscises in the same small patch of liquid.

This carried on for some time and I started to get a bit tired, lying on the ground in the sun, propping up my macro lens with my elbow. Passing Thai people and monks were tolerant and fortunately used to Farangs – foreigners – doing unusual things! They could see that I was photographing butterflies, which all good Buddhists revere.

Unmarked eventually flew off. Then Notch did something I only noticed after I looked closely at these photographs on the computer. The butterfly angled the tip of his abdomen downwards and appeared to deposit a small quantity of liquid on the concrete (below).

I consulted butterfly expert Professor Dick Vane-Wright, who suggested that the butterfly might have been ‘recycling’ something that it has already voided from its anus – the proboscis is reflexed backwards, perhaps to absorb the exudate – a behaviour which Professor Vane-Wright reported that he had seen before in skippers and swallowtails (pers. comm.).

Whatever the significance – or not – of this behaviour, it provides a nice example of glimpses we can get into the lives of insects, by taking photographs. The excellence of modern digital cameras and lens – even relatively inexpensive compact cameras will do – allows us to record behaviour in a way which would have amazed butterfly admirers of old.

1. https://en.wikipedia.org/wiki/Vindula_erota
2. Brakefield, Paul M., and TORBEN B. Larsen. “The evolutionary significance of dry and wet season forms in some tropical butterflies.” Biological journal of the Linnean society 22.1 (1984): 1-12.
3. Ek-Amnuay, Pisuth, and Pramuan Komaradat. Butterflies of Thailand. Amarin Printing and Publishing, 2012.
4. https://rcannon992.com/2013/12/21/thai-cruiser-feeding-on-poinsettia-flowers/